Thread: Issue with multi-threaded tcp server

Hey everyone,

I have a client program that is supposed to send the server two numbers and the server is supposed to return the sum of those numbers. The server has to be multi-threaded because in th context of my project, any number of clients can connect at once. Basically whats happening is if I connect 3 clients to the server, only the last one gets results, and im not really sure why. I've been working on it for a few hours and I can't seem to find the error.

anyway here is the loop where I spawn my threads:

Code:

      while (1)
      {
      /* accept a connection from a client program */
         int newFD;
	pthread_t tid;
			
         newFD = accept( socketFD, (struct sockaddr *)&srcAddr, (socklen_t *)&fromlen );
         if ( newFD < 0 )
         {
            perror( "NATbox:accept()" );
            return -1;
         }
      
         int threadError = pthread_create(&tid, NULL, respond, (void *) newFD); 
         if(threadError < 0)
         {
            perror("NATbox:spawn thread\n");
            return -1;
         }
      }
   	
      int status;
      int i = 0;
      while( i != -1 ) 
      {
         i = wait( &status );
         printf( "Finished pid = %d\n", i );
      }

And here is the function that each thread calls:

Code:

/**
 * function that responds to client requests 
 * adds two numbers received from the client
 * then returns the result
 */
   void * respond( void * incomingRequestFD )
   {
      int buffer[2];
      int retVal = 1;
      int value;
      char response[3];
   	
   	//copy socket 
     int newFD = *(int * ) incomingRequestFD;
   	
      printf("socket: %d\n", newFD);
   	/* receive data from the sender */
      while(retVal != 0 )
      {
         retVal = recv(newFD, buffer, sizeof(buffer), 0);
         if(retVal < 0)
         {
            perror("add_server:recv()");
            exit(1);
         } 	
         printf("received: %d\t%d\n", buffer[0], buffer[1]);
      	/* add the two received numbers together */
         value = buffer[0] + buffer[1];
         printf("value: %d\n", value);
       	/* write the int to the buffer */
         sprintf(response, "%d", value);
      	/* send result to client */
         send(newFD, response, sizeof(response), 0);
      }
   	/* close socket */
      close(newFD);
   
      return 0;
   }/* end respond */

Thanks,
Hunter

I accept a new connection on newFD(a socket), inside my while loop, then pass that socket to the thread function respond. Since the thread only passes void pointers, I cast it back to an int pointer inside the function so I can receive on it.

What is the issue with that? I read this online as a way to use sockets passed using threads.

Hunter